Implant unit delivery tool

ABSTRACT

An implant unit delivery tool is provided. The implant delivery tool may include a body, a holder disposed at a distal end of the body and adapted to hold an implant unit, and an implant activator associated with the body, the implant activator configured to receive power from a power source. The implant activator may be configured to selectively and wirelessly transfer power from the power source to the implant unit during implantation of the implant unit into the body of a subject to cause modulation of at least one nerve in the body of the subject, and determine a degree of nerve modulation response resulting from the selective and wireless transfer of power from the power source to the implant unit claims.

RELATED APPLICATIONS

This application is a continuation-in-part of U.S. patent application Ser. No. 13/952,082, filed Jul. 26, 2013 and U.S. patent application Ser. No. 13/952,031, filed Jul. 26, 2013, and claims the benefit of priority under 35 U.S.C. § 119(e) to U.S. Provisional Application No. 61/836,089, filed Jun. 17, 2013. Each of the above-referenced applications is incorporated herein by reference.

TECHNICAL FIELD

Embodiments of the present disclosure generally relate to devices and methods for modulating a nerve. More particularly, embodiments of the present disclosure relate to devices and methods for delivering an implantable device to a location suitable for neural modulation.

BACKGROUND

Neural modulation presents the opportunity to treat many physiological conditions and disorders by interacting with the body's own natural neural processes. Neural modulation includes inhibition (e.g. blockage), stimulation, modification, regulation, or therapeutic alteration of activity, electrical or chemical, in the central, peripheral, or autonomic nervous system. By modulating the activity of the nervous system, for example through the stimulation of nerves or the blockage of nerve signals, several different goals may be achieved. Motor neurons may be stimulated at appropriate times to cause muscle contractions. Sensory neurons may be blocked, for instance to relieve pain, or stimulated, for instance to provide a signal to a subject. In other examples, modulation of the autonomic nervous system may be used to adjust various involuntary physiological parameters, such as heart rate and blood pressure. Neural modulation may provide the opportunity to treat several diseases or physiological conditions, a few examples of which are described in detail below.

Among the conditions to which neural modulation may be applied are sleep related breathing disorders, such as snoring and obstructive sleep apnea (OSA). OSA is a respiratory disorder characterized by recurrent episodes of partial or complete obstruction of the upper airway during sleep. During the sleep of a person without OSA, the pharyngeal muscles relax during sleep and gradually collapse, narrowing the airway. The airway narrowing limits the effectiveness of the sleeper's breathing, causing a rise in CO₂ levels in the blood. The increase in CO₂ results in the pharyngeal muscles contracting to open the airway to restore proper breathing. The largest of the pharyngeal muscles responsible for upper airway dilation is the genioglossus muscle, which is one of several different muscles in the tongue. The genioglossus muscle is responsible for forward tongue movement and the stiffening of the anterior pharyngeal wall. In patients with OSA, the neuromuscular activity of the genioglossus muscle is decreased compared to normal individuals, accounting for insufficient response and contraction to open the airway as compared to a normal individual. This lack of response contributes to a partial or total airway obstruction, which significantly limits the effectiveness of the sleeper's breathing. In OSA patients, there are often several airway obstruction events during the night. Because of the obstruction, there is a gradual decrease of oxygen levels in the blood (hypoxemia). Hypoxemia leads to night time arousals, which may be registered by EEG, showing that the brain awakes from any stage of sleep to a short arousal. During the arousal, there is a conscious breath or gasp, which resolves the airway obstruction. An increase in sympathetic tone activity rate through the release of hormones such as epinephrine and noradrenaline also often occurs as a response to hypoxemia. As a result of the increase in sympathetic tone, the heart enlarges in an attempt to pump more blood and increase the blood pressure and heart rate, further arousing the patient. After the resolution of the apnea event, as the patient returns to sleep, the airway collapses again, leading to further arousals.

These repeated arousals, combined with repeated hypoxemia, leaves the patient sleep deprived, which leads to daytime somnolence and worsens cognitive function. This cycle can repeat itself up to hundreds of times per night in severe patients. Thus, the repeated fluctuations in and sympathetic tone and episodes of elevated blood pressure during the night evolve to high blood pressure through the entire day. Subsequently, high blood pressure and increased heart rate may cause other diseases.

Snoring in patients is frequently a result of a partially obstructed airway. Some patients experience relaxation of the pharyngeal muscles to a point that involves partial obstruction not significant enough to cause subsequent arousals during sleep. When the pharyngeal muscles relax and narrow the airway, air must travel through the airway at a higher velocity to maintain a similar volumetric flow rate. Higher velocity flows are more likely to be turbulent. These turbulent flows can cause vibrations in the tissue structure of the airway, producing an audible snoring effect. Snoring may have several adverse effects on both sufferers and those around them. Snoring may lead to hypopnea, a condition in which blood oxygen levels are decreased, resulting in shallower, less restful sleep. Snoring may also be associated with an increased risk of stroke and carotid artery atherosclerosis. Additionally, snoring may be detrimental to the sleep of those around the sufferer.

Efforts for treating both snoring and OSA include Continuous Positive Airway Pressure (CPAP) treatment, which requires the patient to wear a mask through which air is blown into the nostrils to keep the airway open. Other treatment options include the implantation of rigid inserts in the soft palate to provide structural support, tracheotomies, or tissue ablation.

Another condition to which neural modulation may be applied is the occurrence of migraine headaches. Pain sensation in the head is transmitted to the brain via the occipital nerve, specifically the greater occipital nerve, and the trigeminal nerve. When a subject experiences head pain, such as during a migraine headache, the inhibition of these nerves may serve to decrease or eliminate the sensation of pain.

Neural modulation may also be applied to hypertension. Blood pressure in the body is controlled via multiple feedback mechanisms. For example, baroreceptors in the carotid body in the carotid artery are sensitive to blood pressure changes within the carotid artery. The baroreceptors generate signals that are conducted to the brain via the glossopharyngeal nerve when blood pressure rises, signaling the brain to activate the body's regulation system to lower blood pressure, e.g. through changes to heart rate, and vasodilation/vasoconstriction. Conversely, parasympathetic nerve fibers on and around the renal arteries generate signals that are carried to the kidneys to initiate actions, such as salt retention and the release of angiotensin, which raise blood pressure. Modulating these nerves may provide the ability to exert some external control over blood pressure.

The foregoing are just a few examples of conditions to which neuromodulation may be of benefit, however embodiments of the invention described hereafter are not necessarily limited to treating only the above-described conditions.

SUMMARY

Some embodiments include an implant unit delivery tool. The implant delivery tool includes a body, a holder disposed at a distal end of the body and adapted to hold an implant unit, and an implant activator associated with the body, the implant activator configured to receive power from a power source. The implant activator may be configured to selectively and wirelessly transfer power from the power source to the implant unit during implantation of the implant unit into the body of a subject to cause modulation of at least one nerve in the body of the subject, and determine a degree of nerve modulation response resulting from the selective and wireless transfer of power from the power source to the implant unit claims.

Additional features of the disclosure will be set forth in part in the description that follows, and in part will be obvious from the description, or may be learned by practice of the disclosed embodiments.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only, and are not restrictive of the invention, as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate several embodiments of the disclosure and, together with the description, serve to explain the principles of the embodiments disclosed herein.

FIG. 1 schematically illustrates an implant unit and external unit, according to an exemplary embodiment of the present disclosure.

FIG. 2 is a partially cross-sectioned side view of a subject with an implant unit and external unit, according to an exemplary embodiment of the present disclosure.

FIG. 3 schematically illustrates a system including an implant unit and an external unit, according to an exemplary embodiment of the present disclosure.

FIG. 4 is a top view of an implant unit, according to an exemplary embodiment of the present disclosure.

FIGS. 5a-b are top views of alternate embodiments of an implant unit, according to exemplary embodiments of the present disclosure.

FIG. 6 illustrates circuitry of an implant unit and an external unit, according to an exemplary embodiment of the present disclosure.

FIG. 7 illustrates a graph of quantities that may be used in determining energy delivery as a function coupling, according to an exemplary disclosed embodiment.

FIG. 8a illustrates a pair of electrodes spaced apart from one another along the longitudinal direction of nerve to facilitate generation of an electric field having field lines substantially parallel to the longitudinal direction of nerve.

FIG. 8b illustrates an embodiment wherein electrodes are spaced apart from one another in a longitudinal direction of at least a portion of nerve.

FIG. 8c illustrates a situation wherein electrodes are spaced apart from one another in a transverse direction of nerve.

FIG. 9 illustrates effects of electrode configuration on the shape of a generated electric field.

FIG. 10 is illustrates additional features of one embodiment of implant unit.

FIG. 11 depicts anatomy of the tongue and associated muscles and nerves.

FIG. 12 illustrates an exemplary implantation position for an implant unit.

FIGS. 13a-13c illustrate various aspects of a delivery tool.

FIGS. 14a-14c illustrates various aspects of a delivery tool.

FIG. 15 depicts features of a delivery tool implant holder portion.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Reference will now be made in detail to exemplary embodiments of the present disclosure, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts.

Embodiments of the present disclosure relate generally to devices for modulating a nerve through the delivery of energy. Nerve modulation, or neural modulation, includes inhibition (e.g. blockage), stimulation, modification, regulation, or therapeutic alteration of activity, electrical or chemical, in the central, peripheral, or autonomic nervous system. Nerve modulation may take the form of nerve stimulation, which may include providing energy to the nerve to create a voltage change sufficient for the nerve to activate, or propagate an electrical signal of its own. Nerve modulation may also take the form of nerve inhibition, which may including providing energy to the nerve sufficient to prevent the nerve from propagating electrical signals. Nerve inhibition may be performed through the constant application of energy, and may also be performed through the application of enough energy to inhibit the function of the nerve for some time after the application. Other forms of neural modulation may modify the function of a nerve, causing a heightened or lessened degree of sensitivity. As referred to herein, modulation of a nerve may include modulation of an entire nerve and/or modulation of a portion of a nerve. For example, modulation of a motor neuron may be performed to affect only those portions of the neuron that are distal of the location to which energy is applied.

In patients that suffer from a sleep breathing disorder, for example, a primary target response of nerve stimulation may include contraction of a tongue muscle (e.g., the muscle) in order to move the tongue to a position that does not block the patient's airway. In the treatment of migraine headaches, nerve inhibition may be used to reduce or eliminate the sensation of pain. In the treatment of hypertension, neural modulation may be used to increase, decrease, eliminate or otherwise modify nerve signals generated by the body to regulate blood pressure.

While embodiments of the present disclosure may be disclosed for use in patients with specific conditions, the embodiments may be used in conjunction with any patient/portion of a body where nerve modulation may be desired. That is, in addition to use in patients with a sleep breathing disorder, migraine headaches, or hypertension, embodiments of the present disclosure may be used in many other areas, including, but not limited to: deep brain stimulation (e.g., treatment of epilepsy, Parkinson's, and depression); cardiac pace-making, stomach muscle stimulation (e.g., treatment of obesity), back pain, incontinence, menstrual pain, and/or any other condition that may be affected by neural modulation.

FIG. 1 illustrates an implant unit and external unit, according to an exemplary embodiment of the present disclosure. An implant unit 110, may be configured for implantation in a subject, in a location that permits it to modulate a nerve 115. The implant unit 110 may be located in a subject such that intervening tissue 111 exists between the implant unit 110 and the nerve 115. Intervening tissue may include muscle tissue, connective tissue, organ tissue, or any other type of biological tissue. Thus, location of implant unit 110 does not require contact with nerve 115 for effective neuromodulation. The implant unit 110 may also be located directly adjacent to nerve 115, such that no intervening tissue 111 exists.

In treating a sleep breathing disorder, implant unit 110 may be located on a genioglossus muscle of a patient. Such a location is suitable for modulation of the hypoglossal nerve, branches of which run inside the genioglossus muscle. Implant unit 110 may also be configured for placement in other locations. For example, migraine treatment may require subcutaneous implantation in the back of the neck, near the hairline of a subject, or behind the ear of a subject, to modulate the greater occipital nerve and/or the trigeminal nerve. Treating hypertension may require the implantation of a neuromodulation implant intravascularly inside the renal artery or renal vein (to modulate the parasympathetic renal nerves), either unilaterally or bilaterally, inside the carotid artery or jugular vein (to modulate the glossopharyngeal nerve through the carotid baroreceptors). Alternatively or additionally, treating hypertension may require the implantation of a neuromodulation implant subcutaneously, behind the ear or in the neck, for example, to directly modulate the glossopharyngeal nerve.

External unit 120 may be configured for location external to a patient, either directly contacting, or close to the skin 112 of the patient. External unit 120 may be configured to be affixed to the patient, for example, by adhering to the skin 112 of the patient, or through a band or other device configured to hold external unit 120 in place. Adherence to the skin of external unit 120 may occur such that it is in the vicinity of the location of implant unit 110.

FIG. 2 illustrates an exemplary embodiment of a neuromodulation system for delivering energy in a patient 100 with a sleep breathing disorder. The system may include an external unit 120 that may be configured for location external to the patient. As illustrated in FIG. 2, external unit 120 may be configured to be affixed to the patient 100. FIG. 2 illustrates that in a patient 100 with a sleep breathing disorder, the external unit 120 may be configured for placement underneath the patient's chin and/or on the front of patient's neck. The suitability of placement locations may be determined by communication between external unit 120 and implant unit 110, discussed in greater detail below. In alternate embodiments, for the treatment of conditions other than a sleep breathing disorder, the external unit may be configured to be affixed anywhere suitable on a patient, such as the back of a patient's neck, i.e. for communication with a migraine treatment implant unit, on the outer portion of a patient's abdomen, i.e. for communication with a stomach modulating implant unit, on a patient's back, i.e. for communication with a renal artery modulating implant unit, and/or on any other suitable external location on a patient's skin, depending on the requirements of a particular application.

External unit 120 may further be configured to be affixed to an alternative location proximate to the patient. For example, in one embodiment, the external unit may be configured to fixedly or removably adhere to a strap or a band that may be configured to wrap around a part of a patient's body. Alternatively, or in addition, the external unit may be configured to remain in a desired location external to the patient's body without adhering to that location.

The external unit 120 may include a housing. The housing may include any suitable container configured for retaining components. In addition, while the external unit is illustrated schematically in FIG. 2, the housing may be any suitable size and/or shape and may be rigid or flexible. Non-limiting examples of housings for the external unit 100 include one or more of patches, buttons, or other receptacles having varying shapes and dimensions and constructed of any suitable material. In one embodiment, for example, the housing may include a flexible material such that the external unit may be configured to conform to a desired location. For example, as illustrated in FIG. 2, the external unit may include a skin patch, which, in turn, may include a flexible substrate. The material of the flexible substrate may include, but is not limited to, plastic, silicone, woven natural fibers, and other suitable polymers, copolymers, and combinations thereof. Any portion of external unit 120 may be flexible or rigid, depending on the requirements of a particular application.

As previously discussed, in some embodiments external unit 120 may be configured to adhere to a desired location. Accordingly, in some embodiments, at least one side of the housing may include an adhesive material. The adhesive material may include a biocompatible material and may allow for a patient to adhere the external unit to the desired location and remove the external unit upon completion of use. The adhesive may be configured for single or multiple uses of the external unit. Suitable adhesive materials may include, but are not limited to biocompatible glues, starches, elastomers, thermoplastics, and emulsions.

FIG. 3 schematically illustrates a system including external unit 120 and an implant unit 110. In some embodiments, internal unit 110 may be configured as a unit to be implanted into the body of a patient, and external unit 120 may be configured to send signals to and/or receive signals from implant unit 110.

As shown in FIG. 3, various components may be included within a housing of external unit 120 or otherwise associated with external unit 120. As illustrated in FIG. 3, at least one processor 144 may be associated with external unit 120. For example, the at least one processor 144 may be located within the housing of external unit 120. In alternative embodiments, the at least one processor may be configured for wired or wireless communication with the external unit from a location external to the housing.

The at least one processor may include any electric circuit that may be configured to perform a logic operation on at least one input variable. The at least one processor may therefore include one or more integrated circuits, microchips, microcontrollers, and microprocessors, which may be all or part of a central processing unit (CPU), a digital signal processor (DSP), a field programmable gate array (FPGA), or any other circuit known to those skilled in the art that may be suitable for executing instructions or performing logic operations.

FIG. 3 illustrates that the external unit 120 may further be associated with a power source 140. The power source may be removably couplable to the external unit at an exterior location relative to external unit. Alternatively, as shown in FIG. 3, power source 140 may be permanently or removably coupled to a location within external unit 120. The power source may further include any suitable source of power configured to be in electrical communication with the processor. In one embodiment, for example the power source 140 may include a battery.

The power source may be configured to power various components within the external unit. As illustrated in FIG. 3, power source 140 may be configured to provide power to the processor 144. In addition, the power source 140 may be configured to provide power to a signal source 142. The signal source 142 may be in communication with the processor 144 and may include any device configured to generate a signal (e.g., a sinusoidal signal, square wave, triangle wave, microwave, radio-frequency (RF) signal, or any other type of electromagnetic signal). Signal source 142 may include, but is not limited to, a waveform generator that may be configured to generate alternating current (AC) signals and/or direct current (DC) signals. In one embodiment, for example, signal source 142 may be configured to generate an AC signal for transmission to one or more other components. Signal source 142 may be configured to generate a signal of any suitable frequency. In some embodiments, signal source 142 may be configured to generate a signal having a frequency of from about 6.5 MHz to about 13.6 MHz. In additional embodiments, signal source 142 may be configured to generate a signal having a frequency of from about 7.4 to about 8.8 MHz. In further embodiments, signal source 142 may generate a signal having a frequency as low as 90 kHz or as high as 28 MHz.

Signal source 142 may be configured for direct or indirect electrical communication with an amplifier 146. The amplifier may include any suitable device configured to amplify one or more signals generated from signal source 142. Amplifier 146 may include one or more of various types of amplification devices, including, for example, transistor based devices, operational amplifiers, RF amplifiers, power amplifiers, or any other type of device that can increase the gain associated one or more aspects of a signal. The amplifier may further be configured to output the amplified signals to one or more components within external unit 120.

The external unit may additionally include a primary antenna 150. The primary antenna may be configured as part of a circuit within external unit 120 and may be coupled either directly or indirectly to various components in external unit 120. For example, as shown in FIG. 3, primary antenna 150 may be configured for communication with the amplifier 146.

The primary antenna may include any conductive structure that may be configured to create an electromagnetic field. The primary antenna may further be of any suitable size, shape, and/or configuration. The size, shape, and/or configuration may be determined by the size of the patient, the placement location of the implant unit, the size and/or shape of the implant unit, the amount of energy required to modulate a nerve, a location of a nerve to be modulated, the type of receiving electronics present on the implant unit, etc. The primary antenna may include any suitable antenna known to those skilled in the art that may be configured to send and/or receive signals. Suitable antennas may include, but are not limited to, a long-wire antenna, a patch antenna, a helical antenna, etc. In one embodiment, for example, as illustrated in FIG. 3, primary antenna 150 may include a coil antenna. Such a coil antenna may be made from any suitable conductive material and may be configured to include any suitable arrangement of conductive coils (e.g., diameter, number of coils, layout of coils, etc.). A coil antenna suitable for use as primary antenna 150 may have a diameter of between about 1 cm and 10 cm, and may be circular or oval shaped. In some embodiments, a coil antenna may have a diameter between 5 cm and 7 cm, and may be oval shaped. A coil antenna suitable for use as primary antenna 150 may have any number of windings, e.g. 4, 8, 12, or more. A coil antenna suitable for use as primary antenna 150 may have a wire diameter between about 0.1 mm and 2 mm. These antenna parameters are exemplary only, and may be adjusted above or below the ranges given to achieve suitable results.

As noted, implant unit 110 may be configured to be implanted in a patient's body (e.g., beneath the patient's skin). FIG. 2 illustrates that the implant unit 110 may be configured to be implanted for modulation of a nerve associated with a muscle of the subject's tongue 130. Modulating a nerve associated with a muscle of the subject's tongue 130 may include stimulation to cause a muscle contraction. In further embodiments, the implant unit may be configured to be placed in conjunction with any nerve that one may desire to modulate. For example, modulation of the occipital nerve, the greater occipital nerve, and/or the trigeminal nerve may be useful for treating pain sensation in the head, such as that from migraines. Modulation of parasympathetic nerve fibers on and around the renal arteries (i.e. the renal nerves), the vagus nerve, and/or the glossopharyngeal nerve may be useful for treating hypertension. Additionally, any nerve of the peripheral nervous system (both spinal and cranial), including motor neurons, sensory neurons, sympathetic neurons and parasympathetic neurons, may be modulated to achieve a desired effect.

Implant unit 110 may be formed of any materials suitable for implantation into the body of a patient. In some embodiments, implant unit 110 may include a flexible carrier 161 (FIG. 4) including a flexible, biocompatible material. Such materials may include, for example, silicone, polyimides, phenyltrimethoxysilane (PTMS), polymethyl methacrylate (PMMA), Parylene C, polyimide, liquid polyimide, laminated polyimide, black epoxy, polyether ether ketone (PEEK), Liquid Crystal Polymer (LCP), Kapton, etc. Implant unit 110 may further include circuitry including conductive materials, such as gold, platinum, titanium, or any other biocompatible conductive material or combination of materials. Implant unit 110 and flexible carrier 161 may also be fabricated with a thickness suitable for implantation under a patient's skin. Implant 110 may have thickness of less than about 4 mm or less than about 2 mm.

Other components that may be included in or otherwise associated with the implant unit are illustrated in FIG. 3. For example, implant unit 110 may include a secondary antenna 152 mounted onto or integrated with flexible carrier 161. Similar to the primary antenna, the secondary antenna may include any suitable antenna known to those skilled in the art that may be configured to send and/or receive signals. The secondary antenna may include any suitable size, shape, and/or configuration. The size, shape and/or configuration may be determined by the size of the patient, the placement location of the implant unit, the amount of energy required to modulate the nerve, etc. Suitable antennas may include, but are not limited to, a long-wire antenna, a patch antenna, a helical antenna, etc. In some embodiments, for example, secondary antenna 152 may include a coil antenna having a circular shape (see also FIG. 4) or oval shape. Such a coil antenna may be made from any suitable conductive material and may be configured to include any suitable arrangement of conductive coils (e.g., diameter, number of coils, layout of coils, etc.). A coil antenna suitable for use as secondary antenna 152 may have a diameter of between about 5 mm and 30 mm, and may be circular or oval shaped. A coil antenna suitable for use as secondary antenna 152 may have any number of windings, e.g. 4, 15, 20, 30, or 50. A coil antenna suitable for use as secondary antenna 152 may have a wire diameter between about 0.01 mm and 1 mm. These antenna parameters are exemplary only, and may be adjusted above or below the ranges given to achieve suitable results.

Implant unit 110 may additionally include a plurality of field-generating implant electrodes 158 a, 158 b. The electrodes may include any suitable shape and/or orientation on the implant unit so long as the electrodes may be configured to generate an electric field in the body of a patient. Implant electrodes 158 a and 158 b may also include any suitable conductive material (e.g., copper, silver, gold, platinum, iridium, platinum-iridium, platinum-gold, conductive polymers, etc.) or combinations of conductive (and/or noble metals) materials. In some embodiments, for example, the electrodes may include short line electrodes, circular electrodes, and/or circular pairs of electrodes. As shown in FIG. 4, electrodes 158 a and 158 b may be located on an end of a first extension 162 a of an elongate arm 162. The electrodes, however, may be located on any portion of implant unit 110. Additionally, implant unit 110 may include electrodes located at a plurality of locations, for example on an end of both a first extension 162 a and a second extension 162 b of elongate arm 162, as illustrated, for example, in FIG. 5. Positioning electrodes on two extensions of elongate arm 162 may permit bilateral hypoglossal nerve stimulation, as discussed further below. Implant electrodes may have a thickness between about 200 nanometers and 1 millimeter. Anode and cathode electrode pairs may be spaced apart by about a distance of about 0.2 mm to 25 mm. In additional embodiments, anode and cathode electrode pairs may be spaced apart by a distance of about 1 mm to 10 mm, or between 4 mm and 7 mm. Adjacent anodes or adjacent cathodes may be spaced apart by distances as small as 0.001 mm or less, or as great as 25 mm or more. In some embodiments, adjacent anodes or adjacent cathodes may be spaced apart by a distance between about 0.2 mm and 1 mm.

FIG. 4 provides a schematic representation of an exemplary configuration of implant unit 110. As illustrated in FIG. 4, in one embodiment, the field-generating electrodes 158 a and 158 b may include two sets of four circular electrodes, provided on flexible carrier 161, with one set of electrodes providing an anode and the other set of electrodes providing a cathode. Implant unit 110 may include one or more structural elements to facilitate implantation of implant unit 110 into the body of a patient. Such elements may include, for example, elongated arms, suture holes, polymeric surgical mesh, biological glue, spikes of flexible carrier protruding to anchor to the tissue, spikes of additional biocompatible material for the same purpose, etc. that facilitate alignment of implant unit 110 in a desired orientation within a patient's body and provide attachment points for securing implant unit 110 within a body. For example, in some embodiments, implant unit 110 may include an elongate arm 162 having a first extension 162 a and, optionally, a second extension 162 b. Extensions 162 a and 162 b may aid in orienting implant unit 110 with respect to a particular muscle (e.g., the genioglossus muscle), a nerve within a patient's body, or a surface within a body above a nerve. For example, first and second extensions 162 a, 162 b may be configured to enable the implant unit to conform at least partially around soft or hard tissue (e.g., nerve, bone, or muscle, etc.) beneath a patient's skin. Further, implant unit 110 may also include one or more suture holes 160 located anywhere on flexible carrier 161. For example, in some embodiments, suture holes 160 may be placed on second extension 162 b of elongate arm 162 and/or on first extension 162 a of elongate arm 162. Implant unit 110 may be constructed in various shapes. Additionally, or alternatively, implant unit 110 may include surgical mesh 1050 or other perforatable material, described in greater detail below with respect to FIG. 10. In some embodiments, implant unit may appear substantially as illustrated in FIG. 4. In other embodiments, implant unit 110 may lack illustrated structures such as second extension 162 b, or may have additional or different structures in different orientations. Additionally, implant unit 110 may be formed with a generally triangular, circular, or rectangular shape, as an alternative to the winged shape shown in FIG. 4. In some embodiments, the shape of implant unit 110 (e.g., as shown in FIG. 4) may facilitate orientation of implant unit 110 with respect to a particular nerve to be modulated. Thus, other regular or irregular shapes may be adopted in order to facilitate implantation in differing parts of the body.

As illustrated in FIG. 4, secondary antenna 152 and electrodes 158 a, 158 b may be mounted on or integrated with flexible carrier 161. Various circuit components and connecting wires (discussed further below) may be used to connect secondary antenna with implant electrodes 158 a and 158 b. To protect the antenna, electrodes, circuit components, and connecting wires from the environment within a patient's body, implant unit 110 may include a protective coating that encapsulates implant unit 110. In some embodiments, the protective coating may be made from a flexible material to enable bending along with flexible carrier 161. The encapsulation material of the protective coating may also resist humidity penetration and protect against corrosion. In some embodiments, the protective coating may include a plurality of layers, including different materials or combinations of materials in different layers.

In some embodiments, all or some of the circuitry components included in implant 110 may be housed in a ceramic housing. Such a housing may be a ceramic clamshell, and may be welded closed with a biocompatible metal such as gold or titanium. A ceramic housing may protect the components of implant 110 from the environment within the body. A ceramic housing may be further encapsulated with a material used for encapsulating the rest of implant unit 110, as described above.

FIG. 5a is a perspective view of an alternate embodiment of an implant unit 110, according to an exemplary embodiment of the present disclosure. As illustrated in FIG. 5a , implant unit 110 may include a plurality of electrodes, located, for example, at the ends of first extension 162 a and second extension 162 b. FIG. 5a illustrates an embodiment wherein implant electrodes 158 a and 158 b include short line electrodes.

FIG. 5b illustrates another alternate embodiment of implant unit 810, according to an exemplary embodiment of the present disclosure. Implant unit 810 is configured such that circuitry 880 is located in a vertical arrangement with secondary antenna 852. Implant unit 810 may include first extension 162 a and second extension 162 b, wherein one or both of the extensions accommodate electrodes 158 a and 158 b.

Also illustrated in FIG. 10 is encapsulated surgical mesh 1050. Surgical mesh 1050 may provide a larger target area for surgeons to use when suturing implant unit 110 into place during implantation. The entire surgical mesh 1050 may be encapsulated by primary capsule 1021, permitting a surgeon to pass a needle through any portion of the mesh without compromising the integrity of implant unit 110. Surgical mesh 1050 may additionally be used to cover suture holes 160, permitting larger suture holes 160 that may provide surgeons with a greater target area. Surgical mesh 1050 may also encourage surrounding tissue to bond with implant unit 110. In some embodiments, a surgeon may pass a surgical suture needle through suture holes 160, located on one extension 162 a of an elongate arm 162 of implant unit 110, through tissue of the subject, and through surgical mesh 1050 provided on a second extension 162 b of elongate arm 162 of implant unit 110. In this embodiment, the larger target area provided by surgical mesh 1050 may facilitate the suturing process because it may be more difficult to precisely locate a suture needle after passing it through tissue. Implantation and suturing procedures may be further facilitated through the use of a delivery tool, described in greater detail below.

Returning to FIGS. 2 and 3, external unit 120 may be configured to communicate with implant unit 110. For example, in some embodiments, a primary signal may be generated on primary antenna 150, using, e.g., processor 144, signal source 142, and amplifier 146. More specifically, in one embodiment, power source 140 may be configured to provide power to one or both of the processor 144 and the signal source 142. The processor 144 may be configured to cause signal source 142 to generate a signal (e.g., an RF energy signal). Signal source 142 may be configured to output the generated signal to amplifier 146, which may amplify the signal generated by signal source 142. The amount of amplification and, therefore, the amplitude of the signal may be controlled, for example, by processor 144. The amount of gain or amplification that processor 144 causes amplifier 146 to apply to the signal may depend on a variety of factors, including, but not limited to, the shape, size, and/or configuration of primary antenna 150, the size of the patient, the location of implant unit 110 in the patient, the shape, size, and/or configuration of secondary antenna 152, a degree of coupling between primary antenna 150 and secondary antenna 152 (discussed further below), a desired magnitude of electric field to be generated by implant electrodes 158 a, 158 b, etc. Amplifier 146 may output the amplified signal to primary antenna 150.

External unit 120 may communicate a primary signal on primary antenna to the secondary antenna 152 of implant unit 110. This communication may result from coupling between primary antenna 150 and secondary antenna 152. Such coupling of the primary antenna and the secondary antenna may include any interaction between the primary antenna and the secondary antenna that causes a signal on the secondary antenna in response to a signal applied to the primary antenna. In some embodiments, coupling between the primary and secondary antennas may include capacitive coupling, inductive coupling, radiofrequency coupling, etc. and any combinations thereof.

Coupling between primary antenna 150 and secondary antenna 152 may depend on the proximity of the primary antenna relative to the secondary antenna. That is, in some embodiments, an efficiency or degree of coupling between primary antenna 150 and secondary antenna 152 may depend on the proximity of the primary antenna to the secondary antenna. The proximity of the primary and secondary antennas may be expressed in terms of a coaxial offset (e.g., a distance between the primary and secondary antennas when central axes of the primary and secondary antennas are co-aligned), a lateral offset (e.g., a distance between a central axis of the primary antenna and a central axis of the secondary antenna), and/or an angular offset (e.g., an angular difference between the central axes of the primary and secondary antennas). In some embodiments, a theoretical maximum efficiency of coupling may exist between primary antenna 150 and secondary antenna 152 when both the coaxial offset, the lateral offset, and the angular offset are zero. Increasing any of the coaxial offset, the lateral offset, and the angular offset may have the effect of reducing the efficiency or degree of coupling between primary antenna 150 and secondary antenna 152.

As a result of coupling between primary antenna 150 and secondary antenna 152, a secondary signal may arise on secondary antenna 152 when the primary signal is present on the primary antenna 150. Such coupling may include inductive/magnetic coupling, RF coupling/transmission, capacitive coupling, or any other mechanism where a secondary signal may be generated on secondary antenna 152 in response to a primary signal generated on primary antenna 150. Coupling may refer to any interaction between the primary and secondary antennas. In addition to the coupling between primary antenna 150 and secondary antenna 152, circuit components associated with implant unit 110 may also affect the secondary signal on secondary antenna 152. Thus, the secondary signal on secondary antenna 152 may refer to any and all signals and signal components present on secondary antenna 152 regardless of the source.

While the presence of a primary signal on primary antenna 150 may cause or induce a secondary signal on secondary antenna 152, the coupling between the two antennas may also lead to a coupled signal or signal components on the primary antenna 150 as a result of the secondary signal present on secondary antenna 152. A signal on primary antenna 150 induced by a secondary signal on secondary antenna 152 may be referred to as a primary coupled signal component. The primary signal may refer to any and all signals or signal components present on primary antenna 150, regardless of source, and the primary coupled signal component may refer to any signal or signal component arising on the primary antenna as a result of coupling with signals present on secondary antenna 152. Thus, in some embodiments, the primary coupled signal component may contribute to the primary signal on primary antenna 150.

Implant unit 110 may be configured to respond to external unit 120. For example, in some embodiments, a primary signal generated on primary coil 150 may cause a secondary signal on secondary antenna 152, which in turn, may cause one or more responses by implant unit 110. In some embodiments, the response of implant unit 110 may include the generation of an electric field between implant electrodes 158 a and 158 b.

FIG. 6 illustrates circuitry 170 that may be included in external unit 120 and circuitry 180 that may be included in implant unit 110. Additional, different, or fewer circuit components may be included in either or both of circuitry 170 and circuitry 180. As shown in FIG. 6, secondary antenna 152 may be arranged in electrical communication with implant electrodes 158 a, 158 b. In some embodiments, circuitry connecting secondary antenna 152 with implant electrodes 158 a and 158 b may cause a voltage potential across implant electrodes 158 a and 158 b in the presence of a secondary signal on secondary antenna 152. This voltage potential may be referred to as a field inducing signal, as this voltage potential may generate an electric field between implant electrodes 158 a and 158 b. More broadly, the field inducing signal may include any signal (e.g., voltage potential) applied to electrodes associated with the implant unit that may result in an electric field being generated between the electrodes.

The field inducing signal may be generated as a result of conditioning of the secondary signal by circuitry 180. As shown in FIG. 6, circuitry 170 of external unit 120 may be configured to generate an AC primary signal on primary antenna 150 that may cause an AC secondary signal on secondary antenna 152. In certain embodiments, however, it may be advantageous (e.g., in order to generate a unidirectional electric field for modulation of a nerve) to provide a DC field inducing signal at implant electrodes 158 a and 158 b. To convert the AC secondary signal on secondary antenna 152 to a DC field inducing signal, circuitry 180 in implant unit 110 may include an AC-DC converter. The AC to DC converter may include any suitable converter known to those skilled in the art. For example, in some embodiments the AC-DC converter may include rectification circuit components including, for example, diode 156 and appropriate capacitors and resistors. In alternative embodiments, implant unit 110 may include an AC-AC converter, or no converter, in order to provide an AC field inducing signal at implant electrodes 158 a and 158 b.

As noted above, the field inducing signal may be configured to generate an electric field between implant electrodes 158 a and 158 b. In some instances, the magnitude and/or duration of the generated electric field resulting from the field inducing signal may be sufficient to modulate one or more nerves in the vicinity of electrodes 158 a and 158 b. In such cases, the field inducing signal may be referred to as a modulation signal. In other instances, the magnitude and/or duration of the field inducing signal may generate an electric field that does not result in nerve modulation. In such cases, the field inducing signal may be referred to as a sub-modulation signal.

Various types of field inducing signals may constitute modulation signals. For example, in some embodiments, a modulation signal may include a moderate amplitude and moderate duration, while in other embodiments, a modulation signal may include a higher amplitude and a shorter duration. Various amplitudes and/or durations of field-inducing signals across electrodes 158 a, 158 b may result in modulation signals, and whether a field-inducing signal rises to the level of a modulation signal can depend on many factors (e.g., distance from a particular nerve to be stimulated; whether the nerve is branched; orientation of the induced electric field with respect to the nerve; type of tissue present between the electrodes and the nerve; etc.).

In some embodiments, the electrodes 158 a and 158 b may generate an electric field configured to penetrate intervening tissue 111 between the electrodes and one or more nerves. The intervening tissue 111 may include muscle tissue, bone, connective tissue, adipose tissue, organ tissue, or any combination thereof. For subjects suffering with obstructive sleep apnea, for instance, the intervening tissue may include the genioglossus muscle.

The generation of electric fields configured to penetrate intervening tissue is now discussed with respect to FIGS. 8a, 8b, 8c , and 9. In response to a field inducing signal, implant electrodes 158 a and 158 b may be configured to generate an electric field with field lines extending generally in the longitudinal direction of one or more nerves to be modulated. In some embodiments, implant electrodes 158 a and 158 b may be spaced apart from one another along the longitudinal direction of a nerve to facilitate generation of such an electric field. The electric field may also be configured to extend in a direction substantially parallel to a longitudinal direction of at least some portion of the nerve to be modulated. For example, a substantially parallel field may include field lines that extend more in a longitudinal direction than a transverse direction compared to the nerve. Orienting the electric field in this way may facilitate electrical current flow through a nerve or tissue, thereby increasing the likelihood of eliciting an action potential to induce modulation.

FIG. 8a illustrates a pair of electrodes 158 a, 158 b spaced apart from one another along the longitudinal direction of nerve 210 to facilitate generation of an electric field having field lines 220 substantially parallel to the longitudinal direction of nerve 210. In FIG. 8a , modulation electrodes 158 a, 158 b are illustrated as line electrodes, although the generation of substantially parallel electric fields may be accomplished through the use of other types of electrodes, for example, a series of point electrodes. Utilizing an electric field having field lines 220 extending in a longitudinal direction of nerve 210 may serve to reduce the amount of energy required to achieve neural modulation.

Naturally functioning neurons function by transmitting action potentials along their length. Structurally, neurons include multiple ion channels along their length that serve to maintain a voltage potential gradient across a plasma membrane between the interior and exterior of the neuron. Ion channels operate by maintaining an appropriate balance between positively charged sodium ions on one side of the plasma membrane and negatively charged potassium ions on the other side of the plasma membrane. A sufficiently high voltage potential difference created near an ion channel may exceed a membrane threshold potential of the ion channel. The ion channel may then be induced to activate, pumping the sodium and potassium ions across the plasma membrane to switch places in the vicinity of the activated ion channel. This, in turn, further alters the potential difference in the vicinity of the ion channel, which may serve to activate a neighboring ion channel. The cascading activation of adjacent ion channels may serve to propagate an action potential along the length of the neuron. Further, the activation of an ion channel in an individual neuron may induce the activation of ion channels in neighboring neurons that, bundled together, form nerve tissue. The activation of a single ion channel in a single neuron, however, may not be sufficient to induce the cascading activation of neighboring ion channels necessary to permit the propagation of an action potential. Thus, the more ion channels in a locality that may be recruited by an initial potential difference, caused through natural means such as the action of nerve endings or through artificial means, such as the application of electric fields, the more likely the propagation of an action potential may be. The process of artificially inducing the propagation of action potentials along the length of a nerve may be referred to as stimulation, or up modulation.

Neurons may also be prevented from functioning naturally through constant or substantially constant application of a voltage potential difference. After activation, each ion channel experiences a refractory period, during which it “resets” the sodium and potassium concentrations across the plasma membrane back to an initial state. Resetting the sodium and potassium concentrations causes the membrane threshold potential to return to an initial state. Until the ion channel restores an appropriate concentration of sodium and potassium across the plasma membrane, the membrane threshold potential will remain elevated, thus requiring a higher voltage potential to cause activation of the ion channel. If the membrane threshold potential is maintained at a high enough level, action potentials propagated by neighboring ion channels may not create a large enough voltage potential difference to surpass the membrane threshold potential and activate the ion channel. Thus, by maintaining a sufficient voltage potential difference in the vicinity of a particular ion channel, that ion channel may serve to block further signal transmission. The membrane threshold potential may also be raised without eliciting an initial activation of the ion channel. If an ion channel (or a plurality of ion channels) are subjected to an elevated voltage potential difference that is not high enough to surpass the membrane threshold potential, it may serve to raise the membrane threshold potential over time, thus having a similar effect to an ion channel that has not been permitted to properly restore ion concentrations. Thus, an ion channel may be recruited as a block without actually causing an initial action potential to propagate. This method may be valuable, for example, in pain management, where the propagation of pain signals is undesired. As described above with respect to stimulation, the larger the number of ion channels in a locality that may be recruited to serve as blocks, the more likely the chance that an action potential propagating along the length of the nerve will be blocked by the recruited ion channels, rather than traveling through neighboring, unblocked channels.

The number of ion channels recruited by a voltage potential difference may be increased in at least two ways. First, more ion channels may be recruited by utilizing a larger voltage potential difference in a local area. Second, more ion channels may be recruited by expanding the area affected by the voltage potential difference.

Returning to FIG. 8a , it can be seen that, due to the electric field lines 220 running in a direction substantially parallel to the longitudinal direction of the nerve 210, a large portion of nerve 210 may encounter the field. Thus, more ion channels from the neurons that make up nerve 210 may be recruited without using a larger voltage potential difference. In this way, modulation of nerve 210 may be achieved with a lower current and less power usage. FIG. 8b illustrates an embodiment wherein electrodes 158 a and 158 are still spaced apart from one another in a longitudinal direction of at least a portion of nerve 210. A significant portion of nerve 210 remains inside of the electric field. FIG. 8c illustrates a situation wherein electrodes 158 a and 158 b are spaced apart from one another in a transverse direction of nerve 210. In this illustration, it can be seen that a significantly smaller portion of nerve 210 will be affected by electric field lines 220.

FIG. 9 illustrates potential effects of electrode configuration on the shape of a generated electric field. The top row of electrode configurations, e.g. A, B, and C, illustrates the effects on the electric field shape when a distance between electrodes of a constant size is adjusted. The bottom row of electrode configurations, e.g. D, E, and F illustrates the effects on the electric field shape when the size of electrodes of constant distance is adjusted.

In embodiments consistent with the present disclosure, modulation electrodes 158 a, 158 b may be arranged on the surface of a muscle or other tissue, in order to modulate a nerve embedded within the muscle or other tissue. Thus, tissue may be interposed between modulation electrodes 158 a, 158 b and a nerve to be modulated. Modulation electrodes 158 a, 158 b may be spaced away from a nerve to be modulated. The structure and configuration of modulation electrodes 158 a, 158 b may play an important role in determining whether modulation of a nerve, which is spaced a certain distance away from the electrodes, may be achieved.

Electrode configurations A, B, and C show that when modulation electrodes 158 a, 158 b of a constant size are moved further apart, the depth of the electric field facilitated by the electrodes increases. The strength of the electric field for a given configuration may vary significantly depending on a location within the field. If a constant level of current is passed between modulation electrodes 158 a and 158 b, however, the larger field area of configuration C may exhibit a lower overall current density than the smaller field area of configuration A. A lower current density, in turn, implies a lower voltage potential difference between two points spaced equidistant from each other in the field facilitated by configuration C relative to that of the field facilitated by configuration A. Thus, while moving modulation electrodes 158 a and 158 b farther from each other increases the depth of the field, it also decreases the strength of the field. In order to modulate a nerve spaced away from modulation electrodes 158 a, 158 b, a distance between the electrodes may be selected in order to facilitate an electric field of strength sufficient to surpass a membrane threshold potential of the nerve (and thereby modulate it) at the depth of the nerve. If modulation electrodes 158 a, 158 b are too close together, the electric field may not extend deep enough into the tissue in order to modulate a nerve located therein. If modulation electrodes 158 a, 158 b are too far apart, the electric field may be too weak to modulate the nerve at the appropriate depth.

Appropriate distances between modulation electrodes 158 a, 158 b, may depend on an implant location and a nerve to be stimulated. For example, modulation point 901 is located at the same depth equidistant from the centers of modulation electrodes 158 a, 158 b in each of configurations A, B, and C, The figures illustrate that, in this example, configuration B is most likely to achieve the highest possible current density, and therefore voltage potential, at modulation point 901. The field of configuration A may not extend deeply enough, and the field of configuration C may be too weak at that depth.

In some embodiments, modulation electrodes 158 a, 158 b may be spaced apart by about a distance of about 0.2 mm to 25 mm. In additional embodiments, modulation electrodes 158 a, 158 b may be spaced apart by a distance of about 1 mm to 10 mm, or between 4 mm and 7 mm. In other embodiments modulation electrodes 158 a, 158 b may be spaced apart by between approximately 6 mm and 7 mm.

Electrode configurations D, E, and F show that when modulation electrodes 158 a, 158 b of a constant distance are changed in size, the shape of the electric field facilitated by the electrodes changes. If a constant level of current is passed between when modulation electrodes 158 a and 158 b, the smaller electrodes of configuration D may facilitate a deeper field than that of configurations E and F, although the effect is less significant relative to changes in distance between the electrodes. As noted above, the facilitated electric fields are not of uniform strength throughout, and thus the voltage potential at seemingly similar locations within each of the electric fields of configurations D, E, and, F may vary considerably. Appropriate sizes of modulation electrodes 158 a, 158 b, may therefore depend on an implant location and a nerve to be stimulated.

In some embodiments, modulation electrodes 158 a, 158 b may have a surface area between approximately 0.01 mm² and 80 mm². In additional embodiments, modulation electrodes 158 a, 158 b may have a surface area between approximately 0.1 mm² and 4 mm². In other embodiments modulation electrodes 158 a, 158 b may have a surface area of between approximately 0.25 mm² and 0.35 mm².

In some embodiments, modulation electrodes 158 a, 158 b may be arranged such that the electrodes are exposed on a single side of carrier 161. In such an embodiment, an electric field is generated only on the side of carrier 161 with exposed electrodes. Such a configuration may serve to reduce the amount of energy required to achieve neural modulation, because the entire electric field is generated on the same side of the carrier as the nerve, and little or no current is wasted traveling through tissue away from the nerve to be modulated. Such a configuration may also serve to make the modulation more selective. That is, by generating an electric field on the side of the carrier where there is a nerve to be modulated, nerves located in other areas of tissue (e.g. on the other side of the carrier from the nerve to be modulated), may avoid being accidentally modulated.

As discussed above, the utilization of electric fields having electrical field lines extending in a direction substantially parallel to the longitudinal direction of a nerve to be modulated may serve to lower the power requirements of modulation. This reduction in power requirements may permit the modulation of a nerve using less than 1.6 mA of current, less than 1.4 mA of current, less than 1.2 mA of current, less than 1 mA of current, less than 0.8 mA of current, less than 0.6 mA of current, less than 0.4 mA of current, and even less than 0.2 mA of current passed between modulation electrodes 158 a, 158 b.

Reducing the current flow required may have additional effects on the configuration of implant unit 110 and external unit 120. For example, the reduced current requirement may enable implant unit 110 to modulate a nerve without a requirement for a power storage unit, such as a battery or capacitor, to be implanted in conjunction with implant unit 110. For example, implant unit 110 may be capable of modulating a nerve using only the energy received via secondary antenna 152. Implant unit 110 may be configured to serve as a pass through that directs substantially all received energy to modulation electrodes 158 a and 158 b for nerve modulation. Substantially all received energy may refer to that portion of energy that is not dissipated or otherwise lost to the internal components of implant unit 110. Finally, the reduction in required current may also serve to reduce the amount of energy required by external unit 120. External unit 120 may be configured to operate successfully for an entire treatment session lasting from one to ten hours by utilizing a battery having a capacity of less than 240 mAh, less than 120 mAh, and even less than 60 mAh.

As discussed above, utilization of parallel fields may enable implant unit 110 to modulate nerves in a non-contacting fashion. Contactless neuromodulation may increase the efficacy of an implanted implant unit 110 over time compared to modulation techniques requiring contact with a nerve or muscle to be modulated. Over time, implantable devices may migrate within the body. Thus, an implantable device requiring nerve contact to initiate neural modulation may lose efficacy as the device moves within the body and loses contact with the nerve to be modulated. In contrast, implant unit 110, utilizing contactless modulation, may still effectively modulate a nerve even if it moves toward, away, or to another location relative to an initial implant location. Additionally, tissue growth and/or fibrosis may develop around an implantable device. This growth may serve to lessen or even eliminate the contact between a device designed for contact modulation and a nerve to be modulated. In contrast, implant unit 110, utilizing contactless modulation, may continue to effectively modulate a nerve if additional tissue forms between it and a nerve to be modulated.

Whether a field inducing signal constitutes a modulation signal (resulting in an electric field that may cause nerve modulation) or a sub-modulation signal (resulting in an electric field not intended to cause nerve modulation) may ultimately be controlled by processor 144 of external unit 120. For example, in certain situations, processor 144 may determine that nerve modulation is appropriate. Under these conditions, processor 144 may cause signal source 144 and amplifier 146 to generate a modulation control signal on primary antenna 150 (i.e., a signal having a magnitude and/or duration selected such that a resulting secondary signal on secondary antenna 152 will provide a modulation signal at implant electrodes 158 a and 158 b).

Processor 144 may be configured to limit an amount of energy transferred from external unit 120 to implant unit 110. For example, in some embodiments, implant unit 110 may be associated with a threshold energy limit that may take into account multiple factors associated with the patient and/or the implant. For example, in some cases, certain nerves of a patient should receive no more than a predetermined maximum amount of energy to minimize the risk of damaging the nerves and/or surrounding tissue. Additionally, circuitry 180 of implant unit 110 may include components having a maximum operating voltage or power level that may contribute to a practical threshold energy limit of implant unit 110. Processor 144 may be configured to account for such limitations when setting the magnitude and/or duration of a primary signal to be applied to primary antenna 150.

In addition to determining an upper limit of power that may be delivered to implant unit 110, processor 144 may also determine a lower power threshold based, at least in part, on an efficacy of the delivered power. The lower power threshold may be computed based on a minimum amount of power that enables nerve modulation (e.g., signals having power levels above the lower power threshold may constitute modulation signals while signals having power levels below the lower power threshold may constitute sub-modulation signals).

A lower power threshold may also be measured or provided in alternative ways. For example, appropriate circuitry or sensors in the implant unit 110 may measure a lower power threshold. A lower power threshold may be computed or sensed by an additional external device, and subsequently programmed into processor 144, or programmed into implant unit 110. Alternatively, implant unit 110 may be constructed with circuitry 180 specifically chosen to generate signals at the electrodes of at least the lower power threshold. In still another embodiment, an antenna of external unit 120 may be adjusted to accommodate or produce a signal corresponding to a specific lower power threshold. The lower power threshold may vary from patient to patient, and may take into account multiple factors, such as, for example, modulation characteristics of a particular patient's nerve fibers, a distance between implant unit 110 and external unit 120 after implantation, and the size and configuration of implant unit components (e.g., antenna and implant electrodes), etc.

Processor 144 may also be configured to cause application of sub-modulation control signals to primary antenna 150. Such sub-modulation control signals may include an amplitude and/or duration that result in a sub-modulation signal at electrodes 158 a, 158 b. While such sub-modulation control signals may not result in nerve modulation, such sub-modulation control signals may enable feedback-based control of the nerve modulation system. That is, in some embodiments, processor 144 may be configured to cause application of a sub-modulation control signal to primary antenna 150. This signal may induce a secondary signal on secondary antenna 152, which, in turn, induces a primary coupled signal component on primary antenna 150.

To analyze the primary coupled signal component induced on primary antenna 150, external unit 120 may include a feedback circuit 148 (e.g., a signal analyzer or detector, etc.), which may be placed in direct or indirect communication with primary antenna 150 and processor 144. Sub-modulation control signals may be applied to primary antenna 150 at any desired periodicity. In some embodiments, the sub-modulation control signals may be applied to primary antenna 150 at a rate of one every five seconds (or longer). In other embodiments, the sub-modulation control signals may be applied more frequently (e.g., once every two seconds, once per second, once per millisecond, once per nanosecond, or multiple times per second). Further, it should be noted that feedback may also be received upon application of modulation control signals to primary antenna 150 (i.e., those that result in nerve modulation), as such modulation control signals may also result in generation of a primary coupled signal component on primary antenna 150.

The primary coupled signal component may be fed to processor 144 by feedback circuit 148 and may be used as a basis for determining a degree of coupling between primary antenna 150 and secondary antenna 152. The degree of coupling may enable determination of the efficacy of the energy transfer between two antennas. Processor 144 may also use the determined degree of coupling in regulating delivery of power to implant unit 110.

Processor 144 may be configured with any suitable logic for determining how to regulate power transfer to implant unit 110 based on the determined degree of coupling. For example, where the primary coupled signal component indicates that a degree of coupling has changed from a baseline coupling level, processor 144 may determine that secondary antenna 152 has moved with respect to primary antenna 150 (either in coaxial offset, lateral offset, or angular offset, or any combination). Such movement, for example, may be associated with a movement of the implant unit 110, and the tissue that it is associated with based on its implant location. Thus, in such situations, processor 144 may determine that modulation of a nerve in the patient's body is appropriate. More particularly, in response to an indication of a change in coupling, processor 144, in some embodiments, may cause application of a modulation control signal to primary antenna 150 in order to generate a modulation signal at implant electrodes 158 a, 158 b, e.g., to cause modulation of a nerve of the patient.

In an embodiment for the treatment of a sleep breathing disorder, movement of an implant unit 110 may be associated with movement of the tongue, which may indicate snoring, the onset of a sleep apnea event or a sleep apnea precursor. Each of these conditions may require the stimulation of the genioglossus muscle of the patient to relieve or avert the event. Such stimulation may result in contraction of the muscle and movement of the patient's tongue away from the patient's airway.

Modulation control signals may include stimulation control signals, and sub-modulation control signals may include sub-stimulation control signals. Stimulation control signals may have any amplitude, pulse duration, or frequency combination that results in a stimulation signal at electrodes 158 a, 158 b. In some embodiments (e.g., at a frequency of between about 6.5-13.6 MHz), stimulation control signals may include a pulse duration of greater than about 50 microseconds and/or an amplitude of approximately 0.5 amps, or between 0.1 amps and 1 amp, or between 0.05 amps and 3 amps. Sub-stimulation control signals may have a pulse duration less than about 500, or less than about 200 nanoseconds and/or an amplitude less than about 1 amp, 0.5 amps, 0.1 amps, 0.05 amps, or 0.01 amps. Of course, these values are meant to provide a general reference only, as various combinations of values higher than or lower than the exemplary guidelines provided may or may not result in nerve stimulation.

In some embodiments, stimulation control signals may include a pulse train, wherein each pulse includes a plurality of sub-pulses. An alternating current signal (e.g., at a frequency of between about 6.5-13.6 MHz) may be used to generate the pulse train, as follows. A sub-pulse may have a duration of between 50-250 microseconds, or a duration of between 1 microsecond and 2 milliseconds, during which an alternating current signal is turned on. For example, a 200 microsecond sub-pulse of a 10 MHz alternating current signal will include approximately 2000 periods. Each pulse may, in turn, have a duration of between 100 and 500 milliseconds, during which sub-pulses occur at a frequency of between 25 and 100 Hz. For example, a 200 millisecond pulse of 50 Hz sub-pulses will include approximately 10 sub-pulses. Finally, in a pulse train, each pulse may be separated from the next by a duration of between 0.2 and 2 seconds. For example, in a pulse train of 200 millisecond pulses, each separated by 1.3 seconds from the next, a new pulse will occur every 1.5 seconds. A pulse train of this embodiment may be utilized, for example, to provide ongoing stimulation during a treatment session. In the context of a sleep breathing disorder, a treatment session may be a period of time during which a subject is asleep and in need of treatment to prevent a sleep breathing disorder. Such a treatment session may last anywhere from about three to ten hours. In the context of other conditions to which neural modulators of the present disclosure are applied, a treatment session may be of varying length according to the duration of the treated condition.

Processor 144 may be configured to determine a degree of coupling between primary antenna 150 and secondary antenna 152 by monitoring one or more aspects of the primary coupled signal component received through feedback circuit 148. In some embodiments, processor 144 may determine a degree of coupling between primary antenna 150 and secondary antenna 152 by monitoring a voltage level associated with the primary coupled signal component, a current level, or any other attribute that may depend on the degree of coupling between primary antenna 150 and secondary antenna 152. For example, in response to periodic sub-modulation signals applied to primary antenna 150, processor 144 may determine a baseline voltage level or current level associated with the primary coupled signal component. This baseline voltage level, for example, may be associated with a range of movement of the patient's tongue when a sleep apnea event or its precursor is not occurring, e.g. during normal breathing. As the patient's tongue moves toward a position associated with a sleep apnea event or its precursor, the coaxial, lateral, or angular offset between primary antenna 150 and secondary antenna 152 may change. As a result, the degree of coupling between primary antenna 150 and secondary antenna 152 may change, and the voltage level or current level of the primary coupled signal component on primary antenna 150 may also change. Processor 144 may be configured to recognize a sleep apnea event or its precursor when a voltage level, current level, or other electrical characteristic associated with the primary coupled signal component changes by a predetermined amount or reaches a predetermined absolute value.

FIG. 7 provides a graph that illustrates this principle in more detail. For a two-coil system where one coil receives a radio frequency (RF) drive signal, graph 200 plots a rate of change in induced current in the receiving coil as a function of coaxial distance between the coils. For various coil diameters and initial displacements, graph 200 illustrates the sensitivity of the induced current to further displacement between the coils, moving them either closer together or further apart. It also indicates that, overall, the induced current in the secondary coil will decrease as the secondary coil is moved away from the primary, drive coil, i.e. the rate of change of induced current, in mA/mm, is consistently negative. The sensitivity of the induced current to further displacement between the coils varies with distance. For example, at a separation distance of 10 mm, the rate of change in current as a function of additional displacement in a 14 mm coil is approximately −6 mA/mm. If the displacement of the coils is approximately 22 mm, the rate of change in the induced current in response to additional displacement is approximately −11 mA/mm, which corresponds to a local maximum in the rate of change of the induced current. Increasing the separation distance beyond 22 mm continues to result in a decline in the induced current in the secondary coil, but the rate of change decreases. For example, at a separation distance of about 30 mm, the 14 mm coil experiences a rate of change in the induced current in response to additional displacement of about −8 mA/mm. With this type of information, processor 144 may be able to determine a particular degree of coupling between primary antenna 150 and secondary antenna 152, at any given time, by observing the magnitude and/or rate of change in the magnitude of the current associated with the primary coupled signal component on primary antenna 150.

Processor 144 may be configured to determine a degree of coupling between primary antenna 150 and secondary antenna 152 by monitoring other aspects of the primary coupled signal component. For example, in some embodiments, a residual signal, or an echo signal, may be monitored. As shown in FIG. 6, circuitry 180 in implant unit 110 may include inductors, capacitors, and resistors, and thus may constitute an LRC circuit. As described in greater detail above, when external unit 120 transmits a modulation (or sub-modulation) control signal, a corresponding signal is developed on secondary antenna 152. The signal developed on secondary antenna 152 causes current to flow in circuitry 180 of implant unit 110, exciting the LRC circuit. When excited the LRC circuit may oscillate at its resonant frequency, related to the values of the L (inductance), R (resistance), and C (capacitance values in the circuit). When processor 144 stops generating the control signal, both the oscillating signal on primary antenna 150 and the oscillating signal on secondary antenna 152 may decay over a period of time as the current is dissipated. As the oscillating signal on the secondary antenna 152 decays, so too does the coupled feedback signal received by primary antenna 150. Thus, the decaying signal in circuitry 180 of implant unit 110 may be monitored by processor 144 of external unit 120. This monitoring may be further facilitated by configuring the circuitry 170 of external unit 120 to allow the control signal generated in primary antenna 150 to dissipate faster than the signal in the implant unit 110. Monitoring the residual signal and comparing it to expect values of a residual signal may provide processor 144 with an indication of a degree of coupling between primary antenna 150 and secondary antenna 152.

Monitoring the decaying oscillating signal in the implant unit 110 may also provide processor 144 information about the performance of implant unit 110. Processor 144 may be configured to compare the parameters of the control signal with the parameters of the detected decaying implant signal. For example, an amplitude of the decaying signal is proportional to the amount of energy remaining in implant unit 110; by comparing an amount of energy transmitted in the control signal with an amount of energy remaining in the implant, processor 144 may determine a level of power consumption in the implant. Further, by comparing a level of power consumption in the implant to a detected amount of tongue movement, processor 144 may determine an efficacy level of transmitted modulation signals. Monitoring the residual, or echo signals, in implant unit 110 may permit the implementation of several different features. Thus, processor 144 may be able to determine information including power consumption in implant unit 110, current delivery to the tissue by implant unit 110, energy delivery to implant unit 110, functionality of implant unit 110, and other parameters determinable through residual signal analysis

Processor 144 may be configured to monitor the residual implant signal in a diagnostic mode. For example, if processor 144 detects no residual signal in implant unit 110 after transmission of a control signal, it may determine that implant unit 110 is unable to receive any type of transmission, and is not functioning. In another potential malfunction, if processor 144 detects a residual signal in the implant that is higher than expected, it may determine that, while implant unit is receiving a transmitted control signal, the transmitted energy is not being transferred to the tissue by electrodes 158 a, 158 b, at an appropriate rate.

Processor 144 may also be configured to implement a treatment protocol including the application of a desired target current level to be applied by the modulation electrodes (e.g., 1 mA). Even if the modulation control signal delivers a signal of constant amplitude, the delivered current may not remain stable. The coupled feedback signal detected by primary antenna 150 may be used as the basis for feedback control of the implant unit to ensure that the implant delivers a stable 1 mA current during each application of a modulation control signal. Processor 144, by analyzing the residual signal in the implant, may determine an amount of current delivered during the application of a modulation control signal. Processor 144 may then increase or decrease the amplitude of the modulation control signal based on the determined information about the delivered current. Thus, the modulation control signal applied to primary antenna 150 may be adjusted until the observed amplitude of the echo signal indicates that the target current level has been achieved.

In some embodiments, processor 144 may be configured to alter a treatment protocol based on detected efficacy during a therapy period. As described above, processor 144 may be configured, through residual signal analysis, to determine the amount of current, power, or energy delivered to the tissue through electrodes 158 a, 158 b. Processor 144 may be configured to correlate the detected amount of tongue movement as a result of a modulation control signal with the amount of power ultimately delivered to the tissue. Thus, rather than comparing the effects of signal transmission with the amount of power or energy transmitted (which processor 144 may also be configured to do), processor 144 may compare the effects of signal transmission with the amount of power delivered. By comparing modulating effects with power delivered, processor 144 may be able to more accurately optimize a modulation signal.

The residual signal feedback methods discussed above may be applied to any of several other embodiments of the disclosure as appropriate. For example, information gathered through residual signal feedback analysis may be included in the information stored in a memory unit and transmitted to a relay or final destination via a transceiver of external unit 120. In another example, the above described residual signal feedback analysis may be incorporated into methods detecting tongue movement and tongue vibration.

In some embodiments, an initially detected coupling degree may establish a baseline range when the patient attaches external unit 120 to the skin. Presumably, while the patient is awake, the tongue is not blocking the patient's airway and moves with the patients breathing in a natural range, where coupling between primary antenna 150 and secondary antenna 152 may be within a baseline range. A baseline coupling range may encompass a maximum coupling between primary antenna 150 and secondary antenna 152. A baseline coupling range may also encompass a range that does not include a maximum coupling level between primary antenna 150 and secondary antenna 152. Thus, the initially determined coupling may be fairly representative of a non-sleep apnea condition and may be used by processor 144 as a baseline in determining a degree of coupling between primary antenna 150 and secondary antenna 152.

As the patient wears external unit 120, processor 144 may periodically scan over a range of primary signal amplitudes to determine current values of coupling. If a periodic scan results in determination of a degree of coupling different from the baseline coupling, processor 144 may determine that there has been a change from the baseline initial conditions.

By periodically determining a degree of coupling value, processor 144 may be configured to determine, in situ, appropriate parameter values for the modulation control signal that will ultimately result in nerve modulation. For example, by determining the degree of coupling between primary antenna 150 and secondary antenna 152, processor 144 may be configured to select characteristics of the modulation control signal (e.g., amplitude, pulse duration, frequency, etc.) that may provide a modulation signal at electrodes 158 a, 158 b in proportion to or otherwise related to the determined degree of coupling. In some embodiments, processor 144 may access a lookup table or other data stored in a memory correlating modulation control signal parameter values with degree of coupling. In this way, processor 144 may adjust the applied modulation control signal in response to an observed degree of coupling.

Additionally or alternatively, processor 144 may be configured to determine the degree of coupling between primary antenna 150 and secondary antenna 152 during modulation. The tongue, or other structure on or near which the implant is located, and thus implant unit 110, may move as a result of modulation. Thus, the degree of coupling may change during modulation. Processor 144 may be configured to determine the degree of coupling as it changes during modulation, in order to dynamically adjust characteristics of the modulation control signal according to the changing degree of coupling. This adjustment may permit processor 144 to cause implant unit 110 to provide an appropriate modulation signal at electrodes 158 a, 158 b throughout a modulation event. For example, processor 144 may alter the primary signal in accordance with the changing degree of coupling in order to maintain a constant modulation signal, or to cause the modulation signal to be reduced in a controlled manner according to patient needs.

More particularly, the response of processor 144 may be correlated to the determined degree of coupling. In situations where processor 144 determines that the degree of coupling between primary antenna 150 and secondary antenna has fallen only slightly below a predetermined coupling threshold (e.g, during snoring or during a small vibration of the tongue or other sleep apnea event precursor), processor 144 may determine that only a small response is necessary. Thus, processor 144 may select modulation control signal parameters that will result in a relatively small response (e.g., a short stimulation of a nerve, small muscle contraction, etc.). Where, however, processor 144 determines that the degree of coupling has fallen substantially below the predetermined coupling threshold (e.g., where the tongue has moved enough to cause a sleep apnea event), processor 144 may determine that a larger response is required. As a result, processor 144 may select modulation control signal parameters that will result in a larger response. In some embodiments, only enough power may be transmitted to implant unit 110 to cause the desired level of response. In other words, processor 144 may be configured to cause a metered response based on the determined degree of coupling between primary antenna 150 and secondary antenna 152. As the determined degree of coupling decreases, processor 144 may cause transfer of power in increasing amounts. Such an approach may preserve battery life in the external unit 120, may protect circuitry 170 and circuitry 180, may increase effectiveness in addressing the type of detected condition (e.g., sleep apnea, snoring, tongue movement, etc.), and may be more comfortable for the patient.

In some embodiments, processor 144 may employ an iterative process in order to select modulation control signal parameters that result in a desired response level. For example, upon determining that a modulation control signal should be generated, processor 144 may cause generation of an initial modulation control signal based on a set of predetermined parameter values. If feedback from feedback circuit 148 indicates that a nerve has been modulated (e.g, if an increase in a degree of coupling is observed), then processor 144 may return to a monitoring mode by issuing sub-modulation control signals. If, on the other hand, the feedback suggests that the intended nerve modulation did not occur as a result of the intended modulation control signal or that modulation of the nerve occurred but only partially provided the desired result (e.g, movement of the tongue only partially away from the airway), processor 144 may change one or more parameter values associated with the modulation control signal (e.g., the amplitude, pulse duration, etc.).

Where no nerve modulation occurred, processor 144 may increase one or more parameters of the modulation control signal periodically until the feedback indicates that nerve modulation has occurred. Where nerve modulation occurred, but did not produce the desired result, processor 144 may re-evaluate the degree of coupling between primary antenna 150 and secondary antenna 152 and select new parameters for the modulation control signal targeted toward achieving a desired result. For example, where stimulation of a nerve causes the tongue to move only partially away from the patient's airway, additional stimulation may be desired. Because the tongue has moved away from the airway, however, implant unit 110 may be closer to external unit 120 and, therefore, the degree of coupling may have increased. As a result, to move the tongue a remaining distance to a desired location may require transfer to implant unit 110 of a smaller amount of power than what was supplied prior to the last stimulation-induced movement of the tongue. Thus, based on a newly determined degree of coupling, processor 144 can select new parameters for the stimulation control signal aimed at moving the tongue the remaining distance to the desired location.

In one mode of operation, processor 144 may be configured to sweep over a range of parameter values until nerve modulation is achieved. For example, in circumstances where an applied sub-modulation control signal results in feedback indicating that nerve modulation is appropriate, processor 144 may use the last applied sub-modulation control signal as a starting point for generation of the modulation control signal. The amplitude and/or pulse duration (or other parameters) associated with the signal applied to primary antenna 150 may be iteratively increased by predetermined amounts and at a predetermined rate until the feedback indicates that nerve modulation has occurred.

Processor 144 may be configured to determine or derive various physiologic data based on the determined degree of coupling between primary antenna 150 and secondary antenna 152. For example, in some embodiments the degree of coupling may indicate a distance between external unit 120 and implant unit 110, which processor 144 may use to determine a position of external unit 120 or a relative position of a patient's tongue. Monitoring the degree of coupling can also provide such physiologic data as whether a patient's tongue is moving or vibrating (e.g, whether the patient is snoring), by how much the tongue is moving or vibrating, the direction of motion of the tongue, the rate of motion of the tongue, etc.

In response to any of these determined physiologic data, processor 144 may regulate delivery of power to implant unit 110 based on the determined physiologic data. For example, processor 144 may select parameters for a particular modulation control signal or series of modulation control signals for addressing a specific condition relating to the determined physiologic data. If the physiologic data indicates that the tongue is vibrating, for example, processor 144 may determine that a sleep apnea event is likely to occur and may issue a response by delivering power to implant unit 110 in an amount selected to address the particular situation. If the tongue is in a position blocking the patient's airway (or partially blocking a patient's airway), but the physiologic data indicates that the tongue is moving away from the airway, processor 144 may opt to not deliver power and wait to determine if the tongue clears on its own. Alternatively, processor 144 may deliver a small amount of power to implant unit 110 (e.g., especially where a determined rate of movement indicates that the tongue is moving slowly away from the patient's airway) to encourage the tongue to continue moving away from the patient's airway or to speed its progression away from the airway.

The scenarios described are exemplary only. Processor 144 may be configured with software and/or logic enabling it to address a variety of different physiologic scenarios with particularity. In each case, processor 144 may be configured to use the physiologic data to determine an amount of power to be delivered to implant unit 110 in order to modulate nerves associated with the tongue with the appropriate amount of energy.

The disclosed embodiments may be used in conjunction with a method for regulating delivery of power to an implant unit. The method may include determining a degree of coupling between primary antenna 150 associated with external unit 120 and secondary antenna 152 associated with implant unit 110, implanted in the body of a patient. Determining the degree of coupling may be accomplished by processor 144 located external to implant unit 110 and that may be associated with external unit 120. Processor 144 may be configured to regulate delivery of power from the external unit to the implant unit based on the determined degree of coupling.

As previously discussed, the degree of coupling determination may enable the processor to further determine a location of the implant unit. The motion of the implant unit may correspond to motion of the body part where the implant unit may be attached. This may be considered physiologic data received by the processor. The processor may, accordingly, be configured to regulate delivery of power from the power source to the implant unit based on the physiologic data. In alternative embodiments, the degree of coupling determination may enable the processor to determine information pertaining to a condition of the implant unit. Such a condition may include location as well as information pertaining to an internal state of the implant unit. The processor may, according to the condition of the implant unit, be configured to regulate delivery of power from the power source to the implant unit based on the condition data.

In some embodiments, implant unit 110 may include a processor located on the implant. A processor located on implant unit 110 may perform all or some of the processes described with respect to the at least one processor associated with an external unit. For example, a processor associated with implant unit 110 may be configured to receive a control signal prompting the implant controller to turn on and cause a modulation signal to be applied to the implant electrodes for modulating a nerve. Such a processor may also be configured to monitor various sensors associated with the implant unit and to transmit this information back to and external unit. Power for the processor unit may be supplied by an onboard power source or received via transmissions from an external unit.

In other embodiments, implant unit 110 may be self-sufficient, including its own power source and a processor configured to operate the implant unit 110 with no external interaction. For example, with a suitable power source, the processor of implant unit 110 could be configured to monitor conditions in the body of a subject (via one or more sensors or other means), determining when those conditions warrant modulation of a nerve, and generate a signal to the electrodes to modulate a nerve. The power source could be regenerative based on movement or biological function; or the power sources could be periodically rechargeable from an external location, such as, for example, through induction.

FIG. 11 illustrates an exemplary implantation location for implant unit 110. FIG. 11 depicts an implantation location in the vicinity of a genioglossus muscle 1060 that may be accessed through derma on an underside of a subject's chin. FIG. 11 depicts hypoglossal nerve (i.e. cranial nerve XII). The hypoglossal nerve 1051, through its lateral branch 1053 and medial branch 1052, innervates the muscles of the tongue and other glossal muscles, including the genioglossus 1060, the hyoglossus, 1062, myelohyoid (not shown) and the geniohyoid 1061 muscles. The myelohyoid muscle, not pictured in FIG. 11, forms the floor of the oral cavity, and wraps around the sides of the genioglossus muscle 1060. The horizontal compartment of the genioglossus 1060 is mainly innervated by the medial terminal fibers 1054 of the medial branch 1052, which diverges from the lateral branch 1053 at terminal bifurcation 1055. The distal portion of medial branch 1052 then variegates into the medial terminal fibers 1054. Contraction of the horizontal compartment of the genioglossus muscle 1060 may serve to open or maintain a subject's airway. Contraction of other glossal muscles may assist in other functions, such as swallowing, articulation, and opening or closing the airway. Because the hypoglossal nerve 1051 innervates several glossal muscles, it may be advantageous, for OSA treatment, to confine modulation of the hypoglossal nerve 1051 to the medial branch 1052 or even the medial terminal fibers 1054 of the hypoglossal nerve 1051. In this way, the genioglossus muscle, most responsible for tongue movement and airway maintenance, may be selectively targeted for contraction inducing neuromodulation. Alternatively, the horizontal compartment of the genioglossus muscle may be selectively targeted. The medial terminal fibers 1054 may, however, be difficult to affect with neuromodulation, as they are located within the fibers of the genioglossus muscle 1061. Embodiments of the present invention facilitate modulation the medial terminal fibers 1054, as discussed further below.

In some embodiments, implant unit 110, including at least one pair of modulation electrodes, e.g. electrodes 158 a, 158 b, and at least one circuit may be configured for implantation through derma (i.e. skin) on an underside of a subject's chin. When implanted through derma on an underside of a subject's chin, an implant unit 110 may be located proximate to medial terminal fibers 1054 of the medial branch 1052 of a subject's hypoglossal nerve 1051. An exemplary implant location 1070 is depicted in FIG. 11.

In some embodiments, implant unit 110 may be configured such that the electrodes 158 a, 158 b cause modulation of at least a portion of the subject's hypoglossal nerve through application of an electric field to a section of the hypoglossal nerve 1051 distal of a terminal bifurcation 1055 to lateral and medial branches 1053, 1052 of the hypoglossal nerve 1051. In additional or alternative embodiments, implant unit 110 may be located such that an electric field extending from the modulation electrodes 158 a, 158 b can modulate one or more of the medial terminal fibers 1054 of the medial branch 1052 of the hypoglossal nerve 1051. Thus, the medial branch 1053 or the medial terminal fibers 1054 may be modulated so as to cause a contraction of the genioglossus muscle 1060, which may be sufficient to either open or maintain a patient's airway. When implant unit 110 is located proximate to the medial terminal fibers 1054, the electric field may be configured so as to cause substantially no modulation of the lateral branch of the subject's hypoglossal nerve 1051. This may have the advantage of providing selective modulation targeting of the genioglossus muscle 1060.

As noted above, it may be difficult to modulate the medial terminal fibers 1054 of the hypoglossal nerve 1051 because of their location within the genioglossus muscle 1060. Implant unit 110 may be configured for location on a surface of the genioglossus muscle 1060. Electrodes 158 a, 158 b, of implant unit 110 may be configured to generate a parallel electric field 1090, sufficient to cause modulation of the medial terminal branches 1054 even when electrodes 158 a, 158 b are not in contact with the fibers of the nerve. That is, the anodes and the cathodes of the implant may be configured such that, when energized via a circuit associated with the implant 110 and electrodes 158 a, 158 b, the electric field 1090 extending between electrodes 158 a, 158 b may be in the form of a series of substantially parallel arcs extending through and into the muscle tissue on which the implant is located. A pair of parallel line electrodes or two series of circular electrodes may be suitable configurations for producing the appropriate parallel electric field lines. Thus, when suitably implanted, the electrodes of implant unit 110 may modulate a nerve in a contactless fashion, through the generation of parallel electric field lines.

Furthermore, the efficacy of modulation may be increased by an electrode configuration suitable for generating parallel electric field lines that run partially or substantially parallel to nerve fibers to be modulated. In some embodiments, the current induced by parallel electric field lines may have a greater modulation effect on a nerve fiber if the electric field lines 1090 and the nerve fibers to be modulated are partially or substantially parallel. The inset illustration of FIG. 11 depicts electrodes 158 a and 158 b generating electric field lines 1090 (shown as dashed lines) substantially parallel to medial terminal fibers 1054.

In order to facilitate the modulation of the medial terminal fibers 1054, implant unit 110 may be designed or configured to ensure the appropriate location of electrodes when implanted. An exemplary implantation is depicted in FIG. 12.

For example, a flexible carrier 161 of the implant may be configured such that at least a portion of a flexible carrier 161 of the implant is located at a position between the genioglossus muscle 1060 and the geniohyoid muscle 1061. Flexible carrier 161 may be further configured to permit at least one pair of electrodes arranged on flexible carrier 161 to lie between the genioglossus muscle 1060 and the myelohyoid muscle. Either or both of the extensions 162 a and 162 b of elongate arm 161 may be configured adapt to a contour of the genioglossus muscle. Either or both of the extensions 162 a and 162 b of elongate arm 161 may be configured to extend away from the underside of the subject's chin along a contour of the genioglossus muscle 1060. Either or both of extension arms 162 a, 162 b may be configured to wrap around the genioglossus muscle when an antenna 152 is located between the genioglossus 1060 and geniohyoid muscle 1061. In such a configuration, antenna 152 may be located in a plane substantially parallel with a plane defined by the underside of a subject's chin, as shown in FIG. 12.

Flexible carrier 161 may be configured such that the at least one pair of spaced-apart electrodes can be located in a space between the subject's genioglossus muscle and an adjacent muscle. Flexible carrier 161 may be configured such that at least one pair of modulation electrodes 158 a, 158 b is configured for implantation adjacent to a horizontal compartment 1065 of the genioglossus muscle 1060. The horizontal compartment 1065 of the genioglossus 1060 is depicted in FIG. 12 and is the portion of the muscle in which the muscle fibers run in a substantially horizontal, rather than vertical, oblique, or transverse direction. At this location, the hypoglossal nerve fibers run between and in parallel to the genioglossus muscle fibers. In such a location, implant unit 110 may be configured such that the modulation electrodes generate an electric field substantially parallel to the direction of the muscle fibers, and thus, the medial terminal fibers 1054 of the hypoglossal nerve in the horizontal compartment.

Some embodiments of the present disclosure may include methods, devices, and tools for the implantation of implant unit 110. FIGS. 13-15 illustrate an exemplary embodiment of a delivery tool for use in the implantation of implant unit 110 and various features thereof. The features illustrated in FIGS. 13-15 may be combined in any suitable fashion in various embodiments consistent with this disclosure. A delivery tool 1301 may be used during an implantation procedure to properly position implant unit 110, to test implant unit 110, and/or to assist a surgeon in securing implant unit 110 to an appropriate internal body structure.

FIGS. 13a-13b illustrate various aspects of delivery tool 1301. In some embodiments, delivery tool 1301 may include a body 1302, a holder 1303 adapted to hold an implant unit, an implant activator 1304, and a power source 1308, such as a battery, associated with the implant activator. Delivery tool 1301 may also include Body 1302 may include a handle formed so as to receive a thumb and at least one forefinger of a user. Holder 1303 may include any structure adapted to hold and release an implant unit. In some embodiments, holder 1303 may be adapted to hold implant unit 110. Holder 1303 may include various components to releasably hold implant unit 110, such as a vacuum element (not shown), or latching element (not shown), etc.

Holder 1303 may also include a pair of jaws 1305 disposed in an opposing relationship as shown in FIG. 13c . The spacing of the opposing jaws 1305 may be adjustable, for example through a tweezer-type movement of the delivery tool 1301. The tweezer-type movement of the delivery tool 1301 may be controlled by ratchet 1406, as shown in FIG. 14a , configured maintain spacing between jaws 1305 when employed. Thus, a user may position implant unit 110 inside jaws 1305, press the jaws 1305 together until implant unit 110 is firmly held in a flexed position, and employ ratchet 1406 to maintain the jaw 1305 spacing. A user, such as a surgeon, may then release pressure on the delivery tool 1301 while the position of the implant unit 110 is maintained. Maintaining a position of the implant unit may be useful prior to an implantation procedure, as a surgeon prepares for the implantation. It may also be useful during an implantation procedure, as a surgeon may be hold implant unit 110 in place with respect to an implantation location as implantation steps are performed.

Ratchet 1406 may be released, for example when implant 110 is within a desired position within the patient, by causing jaws 1305 to open. Implant 110 may then be released from delivery tool 1301 and left within the patient at the implanted location. As shown in FIG. 14a , ratchet 1406 may include various suitable configurations.

In some embodiments, the legs of body 1302 of delivery tool 1301 may have a bend, illustrated in FIG. 14c , proximal to holder 1303. Such a bend, which may allow the body of the tool to be more parallel to the body of the patient during surgery, may create an angle α between the upper and lower portions of body 1302. Angle α may be between 90 and 150 degrees. Angle α may be less than 150 degrees, less than 135 degrees, less than 120 degrees, less than 105 degrees, and approximately equal to 90 degrees. The bend in the implant tool may make it easier for a surgeon to see the implantation area during a surgery.

In some embodiments, the implant tool may be provided with an rotation portion, permitting one portion of the implant tool body 1302 to rotate against another portion. For example, a rotation portion may be provided to make the bend in the implant tool variable. One or more rotation portions may be provided.

The flexed position of the implant unit 110 may be chosen such that the implant unit 110 will substantially conform to a tissue contour when implanted. For example, holder 1303 may hold implant unit 110 in a bent, curved, compressed, or stretched configuration. As shown in FIG. 13c , holder 1303 may hold implant unit 110 such that first extension 162 a of implant holder 110 is maintained substantially against second jaw 1307 and second extension 162 b of implant holder 110 is maintained substantially against first jaw 1306.

Holder 1303 may also include at least one suture guide member 1501, configured to receive surgical sutures. As shown in FIG. 15, a suture guide member 1501 may include a first suture guide portion 1502 and a second suture guide portion 1503 adapted for the insertion of a surgical needle. First suture guide portion 1502 may be disposed on a first side of holder 1303 and second suture guide portion 1503 may be disposed on a second side of holder 1303, wherein the second side is opposite the first side. Therefore, first and second suture guide portions 1502, 1503 may be associated with holder 1303.

First suture guide portion 1502 may include one or more apertures in jaws 1305, and second suture guide portion 1503 may include a curved channel. In one embodiment, first suture guide portion 1502 may include an aperture in first jaw 1306. The channel of second suture guide portion 1503 may include an arcuate shape extending from second jaw 1307. The channel may have a radius of curvature corresponding to a surgical needle. For example, suture guide member 1501 may be shaped so as to receive any type of surgical suture needle, such as ¼ circle, ⅜ circle, ⅝ circle, ½ circle or ½ curved. Suture guide member 1501 may be configured to correspond to suture holes 160 and/or surgical mesh 1050 of implant unit 110, and may thus facilitate an implantation procedure.

During an implantation procedure, implant unit 110 may be positioned to conform to a tissue structure of a subject, and a surgeon may use suture guide member 1501 to appropriately locate and guide a suture needle in order to suture implant unit 110 in place. Suture guide member 1501 may be configured to set a predetermined angle between suture guide member 1501 and a patient's tissue, and therefore may assist the surgeon by permitting the insertion of a suture needle at the predetermined angle. For example, suture guide member 1501 may set an angle of about 90 degrees between suture guide member 1501 and the patient's tissue. In other embodiments, suture guide member 1501 may set an angle of about 60, about 45, or about 30 degrees.

In some embodiments, delivery tool 1301 may include an auto-suture unit to permit the mechanized suturing of implant unit 110 into place. The auto-suture unit may be configured to advance suture thread through holes in implant unit 110, at the command of implant activator 1304, described in greater detail below.

Returning now to FIGS. 13a-c , as described above, delivery tool 1301 may include an implant activator 1304. Implant activator 1304 may be employed as follows during an implantation procedure. Implant activator 1304 may include a primary antenna 1310 and at least one processor in electrical communication with primary antenna 1310 and a power source. Implant activator may further receive information from a nerve modulation response detector, 1350. Nerve modulation response detector 1350 may include, for example, at least one pair electromyography (EMG) electrodes configured to detect muscular activity which may be used by implant activator 1304 to determine nerve modulation. Nerve modulation response detector 1350 may be disposed on a portion of delivery tool 1301 so as to be in contact with the subject during an implantation procedure. For example, nerve modulation response detector 1350 may be disposed on holder 1303, as illustrated in FIG. 13c . In an embodiment where holder 1303 comprises jaws 1305, nerve modulation response detector 1350 may include EMG electrodes positioned on jaws 1305 so as to contact tissue of the subject during an implantation procedure. In alternative embodiments, delivery tool 1301 may include an extension arm 1365 configured to position nerve modulation response detector in a position so as to contact tissue of the subject, as illustrated, e.g. in FIG. 13 b.

Implant activator 1304 may be configured to interact wirelessly with implant unit 110, for example through signals transmitted by primary antenna 1310. Primary antenna 1310 may include any of the antenna structures described herein with respect to primary antenna 152, and may further also include wire wound coil, etched coil, non-laminated wire wound coil and litz wire coil.

Implant activator 1304 may be slideably disposed on delivery tool 1301 such that implant activator 1304 may slide within a track 1314 formed between first and second faces 1315, 1316. Therefore, implant activator 1304 may slide toward and away from an implant 110, disposed between jaws 1305, within track 1314. For example, implant activator 1304 may slide from a first position (FIG. 13a ) to a second position (FIG. 13b ) a predetermined distance along body 1302. It is further contemplated that one or more securing means 1317 may secure and retain implant activator 1340 within track 1314 when sliding up and down along body 1302. Additionally or alternatively, a protrusion 1312 on implant activator 1304 may slide within the groove formed by track 1314. Securing means 1317 and/or protrusion 1312 may selectively lock implant activator 1304 at a predetermined location along body 1302.

A slidable engagement portion 1321 may activate implant activator 1304 causing implant activator 1304 to slide from the first position toward the second position or from the second position toward the first position. For example, slideable engagement portion 1321 may include a trigger or button configured to be engaged by a user. In one embodiment, a user may depress slideable engagement portion 1321 to activate implant activator 1304. Alternatively, implant activator 1304 may be moved from the first position to the second position, and from the second position to the first position, through a pivotal movement facilitated by a pivotal attachment (not shown). It is further contemplated that a user may slide implant activator 1304 into the desired position to move implant activator 1304 along track 1314. A shown in FIGS. 14a -c, implant activator 1304 may include various shapes and depressions configured to conform to a user's fingers or palm. Such may enable easy sliding of implant activator 1304. Other means of shifting implant activator 1304 may also be employed without departing from the disclosed embodiments.

Processor 1340 may be configured to determine and regulate a degree of coupling between activator antenna 1310 and secondary antenna 152. As shown in FIG. 13a , processor 1340 may be located within or on a surface of body 1302 of delivery tool 1301. In alternative embodiments, processor 1340 may be configured for wired or wireless communication from a location external to delivery tool 1301. Processor 1340 may include, for example, one or more integrated circuits, microchips, microcontrollers, and microprocessors, which may be all or part of a central processing unit (CPU), a digital signal processor (DSP), a field programmable gate array (FPGA), or any other circuit known to those skilled in the art that may be suitable for executing instructions or performing logic operations.

Power source 1308 may include may be removably or permanently coupled to body 1302 of delivery tool 1301. For example, as shown in FIG. 13a , power source may be disposed on an outer or inner surface of implant activator 1304. Power source 1308 may in electrical and wireless communication with processor 1340 and activator implant 1310. For example, power source 1308 may be configured to activate various components including activator antenna 1310 and processor 1340 by transferring power to these components. Power source 1308 may include any source of power capable of activating activator antenna 1310 or processor 1340, for example a battery.

Activator antenna 1310 may be in communication with processor 1340 and power source 1308, and configured to interact with and activate secondary antenna 152 on implant 110. Therefore, activator antenna 1310 may be configured to selectively transfer power from power source 1308 to implant unit 110 during an implantation procedure to cause modulation of at least one nerve in the body of a subject prior to final fixation of implant unit 110. Activator antenna 1310 may include any conductive structure configured to create an electromagnetic field. Activator antenna 1310 may be of any suitable size, shape, and/or configuration. The size, shape, and/or configuration may be determined by the size of the patient, the placement location of implant unit 110, the size and/or shape of implant unit 110, the amount of energy required to activate implant unit 110, the type of receiving electronics present on implant unit 110, etc.

Activator antenna 1310 may include any suitable antenna known to those skilled in the art that may be configured to send and/or receive signals. Suitable antennas may include, but are not limited to, a long-wire antenna, a patch antenna, a helical antenna, etc. In one embodiment, for example, activator antenna 1310 may include a coil antenna. Such a coil antenna may be made from any suitable conductive material and may be configured to include any suitable arrangement of conductive coils (e.g., diameter, number of coils, layout of coils, etc.). A coil antenna suitable for use as activator antenna 1310 may have a diameter of between about 0.1 cm and 10 cm, and may be circular or oval shaped, among other suitable shapes. In some embodiments, activator antenna 1310 may have a diameter between 0.5 cm and 2 cm, and may be oval shaped. A coil antenna suitable for use as activator antenna 1310 may have any number of windings, e.g. 4, 8, 12, or more. A coil antenna suitable for use as activator antenna 1310 may have a wire diameter between about 0.001 mm and 2 mm. These antenna parameters are exemplary only, and may be adjusted above or below the ranges given to achieve suitable results. It is further contemplated that activator antenna 1310 may include the same antenna as secondary antenna 152.

During an exemplary implantation procedure, a surgeon may use delivery tool 1301 to position implant unit 110 in a prospective implantation location and may engage jaws 1305 to bend implant unit 110 such that it substantially conforms to the tissue at the prospective implantation location. The prospective implantation location may be a position suitable for nerve modulation. A surgeon may then shift implant activator 1304 from a first position as shown in FIG. 13a to a second position as shown in FIG. 13b . A slidable engagement portion 1320 of delivery tool body 1301 may be used to slide implant activator 1304 from a first position to a second position. Alternatively, implant activator 1304 may be moved from a first position to a second position through a pivotal movement facilitated by a pivotal attachment (not shown). Other means of shifting an implant activator from a first position to a second position may also be employed without departing from the disclosed embodiments. Moving the implant activator 1304 from a first position to a second position has the effect of bringing primary antenna 1310 into proximity with a secondary antenna 152 of implant unit 110. When energized in a second position, primary antenna 1310 may transfer power to implant unit 110, through, for example, radiofrequency transmission.

Power transmission between primary antenna 1310 and secondary antenna 152 may be enabled by actuator 1320, illustrated in FIG. 13b as a button on the handle of implant tool 1301. Actuator 1320, however, may refer to any device that activates the power sent to the implant activator. The device may include a switch with on/off position that can be positioned on the body of the delivery tool, in a manner that the surgeon can engage the switch to “on” position to deliver power to the implant activator. The actuator may act as a safety barrier to prevent any accidental activation of the implant activator. The actuator may also be located outside the delivery tool and may include, for example, a cable to be connected with the implant activator. In some embodiments, the power source of implant activator 1304 may include a battery integrated into implant activator 1304.

After shifting the implant activator from a first position to a second position, a surgeon may enable power transmission between primary antenna 1310 and a secondary antenna 152 of implant unit 110 to test the functionality of implant unit 110. Implant activator 1304 may include a processor and circuitry having any or all of the functionality previously described with respect to the processor 144 and circuitry 170 of external unit 120. In some embodiments, implant activator 1304 may include a processor and circuitry similar to or identical to that of an external unit 120, with the components shifted only for space considerations. In alternative embodiments, implant activator 1304 includes a processor configured particularly for testing implant unit 110.

Once activated by implant activator 1304, implant unit 110 may be tested via feedback to implant activator 1304 and through observation of patient response. That is, a surgeon may determine that a prospective implant location is suitable based on whether signals applied to the activation modulation electrodes 158 a, 158 b, of implant unit 110 effectively modulate patient nerves. For example, when placing an implant unit 110 for treatment of a sleep breathing disorder, a surgeon may determine a prospective implantation location by observing a patient's tongue movement during power transmission. In other examples, a surgeon may use an endoscope to observe airway dilation. In some embodiments, nerve modulation response detector 1350 may be engaged to detect a nerve modulation response and to permit implant activator 1304 to determine a degree of nerve modulation response resulting from the application of power to implant unit 110. In an embodiment in which nerve modulation response detector includes EMG electrodes, the EMG electrodes may be engaged to measure neuromuscular activity occurring as a result of the modulation caused by implant unit 110.

Implant activator 1304 may be further configured to permit the release of implant unit 110 from implant delivery tool 1301 when a threshold degree of nerve modulation is determined. Thus, implant activator 1304 may be configured so as not to permit the release of implant unit 110 until effective nerve modulation, as indicated by the determination of a threshold degree, is achieved. In some embodiments, implant activator 1304 may be configured with lights or audio devices to alert a surgeon that a threshold degree of nerve modulation has been achieved. After determining that a prospective implantation location constitutes a suitable modulation position, the surgeon may then secure the implant unit 110 in position with sutures.

Implant activator 1304 may also be used to verify the functionality of implant unit 110 prior to the beginning of an implantation procedure. A surgeon may prepare delivery tool 1301 with an implant unit 110 as described above, and shift implant activator 1304 from a first position to a second position without having positioned implant unit 110 in the body. In this method, the surgeon may then activate implant unit 110 to verify that implant unit 110 does not suffer from manufacturing defects. Implant activator 1304 may use, for example, coupling detection techniques described herein in order to verify the functionality of implant unit 110. A result of such verification may be outputted via an audio output, a visual output, and/or a tactile output, for example.

Other embodiments of the present disclosure will be apparent to those skilled in the art from consideration of the specification and practice of the present disclosure.

While this disclosure provides examples of the neuromodulation delivery devices employed for the treatment of certain conditions, usage of the disclosed neuromodulation delivery devices is not limited to the disclosed examples. The disclosure of uses of embodiments of the invention for neuromodulation are to be considered exemplary only. In its broadest sense, the invention may be used in connection with the treatment of any physiological condition through neuromodulation. Alternative embodiments will become apparent to those skilled in the art to which the present invention pertains without departing from its spirit and scope. Accordingly, the scope of the present invention is defined by the appended claims rather than the foregoing description. 

What is claimed is:
 1. A device for testing a sleep apnea implant during an implantation procedure, comprising: an implant activator configured to selectively transfer power to the sleep apnea implant during the implantation procedure to cause modulation of at least one hypoglossal nerve prior to final fixation of the sleep apnea implant to tissue, wherein the implant activator includes a power source, the power transferred to the sleep apnea implant is supplied by the power source, the power source is configured to wirelessly transfer power from the power source to the sleep apnea implant, and the implant activator is selectively moveable toward and away from the sleep apnea implant; and a slideable engagement portion configured to activate the implant activator to cause the implant activator to move from a first position at a first end of a track to a second position a predetermined distance at a second end of the track along a body of the device.
 2. The device of claim 1, wherein the power source includes a battery.
 3. The device of claim 1, wherein the implant activator includes a processor configured to regulate the power transfer to the sleep apnea implant.
 4. The device of claim 1, wherein the implant activator is configured to transfer the power to the sleep apnea implant through radiofrequency transmission.
 5. The device of claim 1, wherein the slideable engagement portion includes a trigger configured to be engaged by a user to activate the implant activator. 